Candidate ccbaab5a84; production candidate validated in real Vite web client 1280x800 on Linux x64, Node24.21.0, Claude2.1.303.
Thread [isolated fixture]; separate A/B config/history directories; Full access.
00:29:40 selected A and sent Reply only A ready; A answered A ready.
00:30:00 same-instance A send launched native Agent run_in_background sleep60 then /tmp/issue-20343-verified-marker.txt; parent finished background launched.
00:30:22 selected B, confirmed picker shows Triage Claude B, sent Reply only B verified.
00:30:32 send refused; composer retains message, handoff pending. Persisted owner remains a. A PID1360956 still alive, cwd [isolated worktree]/apps/server. No new run or detach event from rejected send. Native subagent still running.
Server rejection: The previous provider is still running background agents or commands, and switching would end them. Wait for them to finish, or press Stop, then send the message again.
00:31:25 marker exists with contents A finished safely; native Agent then reports Finished and A delivers its completion message.
00:33 retry retained B message after completion: browser shows B verified.
00:33:31 A PID1360956 no longer exists. Persisted provider-session.detach effect succeeded and provider-turn.start succeeded. No server restart between refusal and successful retry.
Result: pending native work survives refused handoff; after completion old runtime exits and B answers.